This invention relates to an entoptoscopic instrument for observing the interior of an eye and, in particular, to an entoptoscopic instrument for use in intraocular lens implant surgery,
It is a recent trend that cataract surgery and intraocular lens implant surgery have been widely performed. This also brings about a considerable increase in the frequency of secondary implant of an intraocular lens and fixation of a loop of the intraocular lens to the ciliary sulcus. It is to be noted that the ciliary sulcus is situated at the rear the iris and is not directly visible during such surgery. Hence, the intraocular lens must be fixed to the ciliary sulcus without it being visible. In this connection, an expert technique is required to fix the loop and to pass a needle. At present, it is a general practice to also perform peripheral iridectomy on such fixation or to use an endoscope. However, if the peripheral iridectomy is additionally performed, an extra operation is required by the surgeon. On the other hand, when the endoscope is used, the surgeon must monitor a display device located at a position completely different from the part which is operated, during a surgical operation. This adds to the burden imposed on the surgeon.
In Japanese Utility Model Prepublication No. 19106/1984, a dental observation mirror which has a lamp has been proposed and is generally called a "dental mirror". However, this mirror is not suitable for ophthalmological surgery due to its size and luminous energy.
On the other hand, dental stomatoscopes with an illuminator have been proposed in Japanese Utility Model Publications Nos. 22477/1978 and 22478/1978. In both of the dental stomatoscopes, light is emitted from an external light source and guided through a fiberscope (optical fiber) to illuminate a desired part. The light source is generally composed of a halogen lamp. The halogen lamp has a spectral characteristic spreading over a wide wavelength range from an ultraviolet region to infrared region.
If illumination light emitted from the halogen lamp is used in ophthalmologic surgery, an ophthalmic defect is undesirably produced in the eye due to the particular wavelength components of, for example, less than 440 nm contained in the illumination light.
For example, consideration will be directed to a patient of aphakia whose eye lacks a crystalline lens after cataract surgery is performed. It is noted here that such a crystalline lens in a normal eye serves to prevent wavelength components in the ultraviolet band from arriving onto the retina and to reduce the amount of wavelength components which arrives on the retina in a visible violet-blue band.
In the case of the aphakia patient, the ultraviolet and visible violet-blue wavelength components directly arrive on a retina through the eye of the aphakia patient without any substantial reduction. This gives rise to an abnormal condition or damage of a retinal cell which may be called retinal damage by blue light. In addition, the infrared components could cause thermal degeneration to occur in ophthalmic tissue.